Process and device for the preparation of soot from hydrocarbons



June 19, 1962 G. BUTENUTH ETAL 3,039,852

PROCESS AND DEVICE FOR THE PREPARATION OF SOOT FROM HYDROCARBONS Original Filed Jan. 25, 1955 32 63 30 f 4 I7 36 +i f 19 I 26 j I Z INVENTORS 6 11711121 23 atenafiv JiuriMe lieruiorjf ATTORNEYS United States Patent 3,039,852 PROCESS AND DEVICE FOR THE PREPARATION OF SOOT FROM HYDROCARBONS Giinter Butenuth, Knapsack, near Koln, and Kurt Meltendorf, Rolandseck (Rhine), Germany, assignors to Knapsack-Griesheim Aktiengesellschaft, Knapsack, near Koln, Germany, a German company Continuation of application Ser. No. 484,006, Jan. 25,

1955. This application Dec. 17, 195% Ser. No. 10,525 Claims priority, application Germany Feb. 13, 1954 3 Claims. (Cl. 23209.7)

The present invention relates to a process and a device for the preparation of soot from hydrocarbons, this invention being a continuation application of our copending application Serial No. 484,006, filed on January 25, 1955, and now abandoned, for Process and Device for the Preparation of Soot From Hydrocarbons.

it is known to prepare carbon or soot by splitting hydrocarbons under pressure. Hydrocarbons such as gaseous acetylene are compressed for the preparation of soot and decomposed by means of a source of ignition, whereby the carbon separates in the form of soot while hydrogen escapes. The device required for these operations work in such a way that the decomposition is generally effected under a gauge pressure of a few atmospheres, for instance 4-5 atmospheres,'in a vessel, splitting tube or the like, from which, after an adequate time of cooling, the soot is discharged by rinsing with hydrogen with the aid of a blower.

There are also known processes for the preparation of soot from hydrocarbons in the presence of oxygen during which the soot obtained is ejected after decomposition from the reaction vessel by means of the reaction gases formed. Single explosions are brought about in very rapid sequence, whereby, after each explosion, the soot obtained is removed from the reaction vessel by rapidly expanding the reaction gases being under pressure.

These processes show the disadvantage that, in order to obtain the desired bulk weight, the soot has to be subjected to a further mechanical treatment after being blown out of the splitting tube. Another disadvantage is the long time of cooling of the tube necessary after each reaction as well as the subsequent rinsing required with gaseous hydrogen.

Consequently, the processes hitherto known require also, in view of the subsequent compression of the soot, comparatively low productive capacity. In addition, there is increased cost of installation owing to the additional requirements concerning gasometers and blowers.

Now, we have found that the disadvantages of the known processes for the preparation of carbon or soot from hydrocarbons, especially from acetylene or mixtures of acetylene and hydrocarbons, can be avoided according to the invention by decomposing the hydrocarbons under pressure in a splitting room in the absence of oxygen allowing the so formed soot to settle and then discharging the splitting room without additional rinsing by the pressure of the hydrogen formed during the decomposition.

The above mentioned mixtures of acetylene and hydrocarbons may contain, in addition to acetylene, for instance also oil gas. Instead of acetylene there may be used ethylene, propylene, butane or butylene. However, acetylene is used for preferance. In the following, the invention is described with reference to acetylene by way of example only.

The process according to the invention can be carried out by discharging the splitting apparatus by suddenly opening the outlet valve after forming of the soot while cooling the mixture of hydrogen and soot in a cooler installed behind the splitting tube. The sudden discharge 3,039,852 Patented June 19, 1962 from the splitting apparatus produces the desired bulk weight of the soot without a subsequent treatment by alteration of the discharge opening of the outlet valve. The same result can also be achieved in the case of sudden discharge from the splitting apparatus by producing the desired bulk weight of the soot by fitting devices reducing the cross section of the exhaust gas pipe and avoiding a subsequent treatment.

The device for carrying out the process according to the invention consists of a splitting apparatus in the form of a tube with an inlet valve for acetylene, an outlet means such as a valve for the reaction products soot and hydrogen, a sparking plug for splitting the acetylene, a cooler for the reaction products, a soot-collecting vessel, a sack-filling chute for the discharge of the soot and a filter for the purification of the escaping hydrogen. It is of special advantage if the splitting tube is installed in an upright position and is polished inside. It is likewise advantageous if, prior to polishing, the interior of the splitting tube is coated with a hard metal layer.

When carrying out the process according to the present invention it has been found that the soot formed can be removed completely by rapidly expanding the hydrogen. The known processes comprise also the removal of the soot formed by expanding the reaction gases but these gases consist of carbon dioxide, steam, and, in certain cases, of nitrogen, while in the case of the process of the present invention the reaction gas consists solely of pure hydrogen. When preparing soot from hydrocarbons in the presence of oxygen, the pressures produced by the explosion are not nearly as high as in the case of the decomposition of pure acetylene under pressure. The reason is that, when applying oxygen, a decrease in volume is brought about by partial combustion; in the absence of oxygen, however, this is not the case. When preparing soot from acetylene by splitting under pressure it is of extreme importance that no soot at all remains in the tube or on the walls. When refilling the splitting tube with acetylene, these residues can, by ignition by incan descence, lead to an early decomposition of the gas, whereby detonations may occur with uncontrollable high pressures. For this reason, the complete removal of all glowing soot particles which remain is indispensable. Up to the present day rinsing with hydrogen for the total removal of all residues of soot has been deemed absolutely necessary. When carrying out the process according to the present invention, it has been found that the removal of the soot by expanding the hydrogen above the soot, being favored by the upright position of the tube and the polished and hard chromium-plated inner Walling, is complete.

The invention is elucidated by FIGURES l, 2 and 3 of the drawing. FIG. 1 represents a splitting apparatus in form of a tube with auxiliary apparatus. FIG. 2 represents a special construction of the narrowed discharge opening for the soot, and FIG. 3 shows the splitting apparatus with automatic control of valves and switches.

For the preparation of soot (cf. FIG. 1) gaseous hydrocar'oons, for instance acetylene, mixtures of acetylene and oil gas or other mixtures of hydrocarbons are pressed by means of a compressor (not shown) through the inlet valve 2, into the splitting tube 1 where they are compressed, the outlet valve 3 remaining closed. After filling of the splitting tube 1 until the pressure required for the decomposition is reached, the inlet valve 2 is closed and the decomposition brought about by means of the spark plug 4. Immediately after the decomposition, the soot produced settles in the lower part of the splitting tube 1 above the outlet valve 3, whereupon the latter is opened and the hot hydrogen-soot mixture passes under pressure through the cooler 5 into the soot collecting vessel 6. From' here, the hydrogen escapes through a filter 8, while the finished product is drawn off at the sacking slide 7. Thus, the time of cooling in the splitting tube normally lasting several minutes is avoided and reduced to a few seconds settling time. The soot which has settled in the lower part of the splitting tube is ejected solely by the pressure of the hydrogen above the soot, for which purpose the splitting tube is fitted in an upright position. This ejection by pressure guarantees the complete emptying of the splitting tube in the shortest time and makes possible at the same time the preparation of soot of any desired bulk weight ranging from 80 to 100 grams/liter and above, which is achieved by alteration ofthe discharge opening at the outlet valve and whereby every aftertreatment of the product becomes quite superfluous. It has proved to be of advantageto replace the valve by a slide according to FIG. 2 which may possess replaceable discharge openings 9 of various sizes. The installation of a bafile plate, for instance of a shutter or a nozzle, into the discharge pipe of the splitting tube or at the entrance of the soot collecting vessel has likewise proved good. The sudden opening of the outlet valve is, above all, of importance.

It has been found for instance, that, when employing a splitting tube of 200 mm. internal diameter and a discharge pipe of 100 mm. internal diameter, the bulk weight of the soot amounts to 32 grams/liter. A reduction of the cross section to an internal diameter of mm. produced a bulk weight of 91 grams/liter, whilst, when the diameter of the discharge pipe corresponds to that of the splitting tube, a bulk weight of grams/ liter is achieved.

The valves can be controlled by hand, mechanically, pneumatically or electrically. However, the valve of the discharge device should preferably be controlled pneumatically or electrically on account of the sudden open- 1ng.

In order to avoid the adhesion of smallest soot particles to the inner walling of the splitting tube, this has to be polished or previously chromium plated and then polished. In order to avoid local overheating, the outlet valve may be water-cooled. In addition, it is of advantage to install a thermoregulator generally known in the industry at those places of the splitting tube which show the highest temperature. This regulator contributes to the security of the splitting process by cutting oil the supply of acetylene and other hydrocarbons when the maximum temperature, which amounts to about 200 C., is reached. 7 When using suitable and known control members, the valves and the various switches can be operated automatically by cam or cylinder regulation. This has the advantage, as experiments have shown, that the quality of the soot in respect of its empyreumatic constituents, its fine granularity, structure, and electric conductivity, is influenced favorably to a great extent by the uniformity of servicing operation in the single stages of the process.

Since it is very diflicult and costly to carry out operations by hand continuously with observation of precisely specified, partly very short periods, it is of great advantage to carry out all operations required for servicing the splitting tube automatically in a uniform manner and to eliminate all servicing errors, whereby staff and installation costs are reduced and risks are diminished.

This result is attained by automatically steering and controlling all servicing operations by means of known devices which are independent of manual operation.

The device for carrying out this process comprises a compressor for compressing the gas to a specified maximum pressure which can be adjusted automatically, a tube serving as storage room which is provided at the inlet and outlet for the gas with an automatically controlled closing mechanism, a splitting tube the upper part of which is provided with an automatically controlled spark plug and the lower part with a likewise automatically controlled discharge member for the hydrogen 4 and soot formed by the splitting process, and a soot collector. All switches of this device are operated automatically by an electric or pneumatic method from a central point, i.e. from a controller cylinder the speed of which can be adjusted as desired.

By means of the centrally steering controller cylinder the periods for the single operations and intervals are timed .as follows: In a splitting process lasting for one minute there may be used, for instance, 5 seconds for filling the splitting tube, 1 second as safety interval, /2 second for the ignition of the gas, 48 seconds for the cooling and settling of the soot, 3 seconds for blowing the soot formed from the splitting tube, and 2 /2 seconds as safety interval.

The process and device are further elucidated by FIG. 3.

Compressor 10 sucks in the acetylene at 11 and presses it through pipe 12 into the storage tube 13. When the desired gauge pressure has been reached in storage tube 13, overflow valve 14 opens and compressor 10 operates in a cycle. After opening inlet valve 15, the gas, which is contained in storage tube 13 under snperatmospheric pressure, passes into splitting tube 16. The pressure in storage tube 13 should be so high that inlet valve 15 need only be opened for a few seconds in order to attain an equalization of pressure between the storage tube and the splitting tube. Inlet valve 15, ignition by spark plug 17 and outlet valve 18 are operated electropneumatically by an electric controller at equal intervals and for equal periods.

The following example serves to illustrate the invention, but it is not intended to limit it thereto:

Example Storage tube 13 is filled with acetylene gas by means of compressor 10 until a gauge pressure of 15 atmospheres is reached. A higher pressure is prevented by an overflow valve 14 which is adjusted to blow oif at a gauge pressure of 15 atmospheres, so that this pressure is maintained in the storage tube. Controller cylinder 19 is driven by a synchronous motor and revolves once a minute, so that the staggered points of contact on the cylinder also operate once a minute and cause the auxiliary members such as inlet valve 15, spark plug 17, and outlet valve 18 to work likewise once every minute. When the controller cylinder 19 rotates, the current collector 20 first comes into contact with contact point 21 on the cylinder. The circuit is hereby closed and magnet 24 opens a compressed-air valve 22 of known type, so that the compressed air coming from 23 can pass piston 25 and open the valve for 5 seconds which time suffices to attain an equalization of pressure between storage tube 13 and splitting tube 16. In the present example, the volume of the storage tube in proportion to the volume of the splitting tube is such, that after equalization of pressure in storage and splitting tubes, :1 gauge pressure of 10 atmospheres is exerted on the acetylene. Cylinder 19 moves on, current collector 20 leaves contact point 21, and magnet 24 becomes currentless. The control piston at 22 drops and lets the compressed air coming from 23 pass under the piston 25, whereby valve 15 is again closed. Dur ing this time, magnet 26 which controls the control member 27 operating outlet valve 18 is without current. Since this valve is operated in the same way as inlet valve 15, it is always closed when the magnet is currentless.

After completion of the filling process a gauge pressure of 10 atmospheres is exerted on the acetylene contained in the splitting tube 16. All valves are closed. After an interval of one second, current collector 28 comes into contact with point 29, thus setting a spark plug working which causes the acetylene on which a pressure is exerted in the splitting tube to decompose. After half a second, while the cylinder rotates, the ignition is cut 01f, which operation is followed by an interval of 48 Seconds, during which time the soot can cool down and settle. Thereupon valve 18 opens the 3 seconds in the same way as described for valve 15, the soot is blown into soot collector 30, valve 18 closes again, :and after a safety interval of 2 seconds, the cycle begins all over again with the opening of the inlet valve. Thus all servicing directions are strictly adhered to during the cycle. After filling of the splitting tube which requires 5 seconds, 55 seconds may be used for refilling the storage tube, that is to say that the compressor is not idling during these 55 seconds, so that its capacity needs only correspond to the desired production of soot.

The following switching periods and intervals are suitable for a switching process lasting one minute:

5 seconds, filling the splitting tube 1 second, safety interval /2 second, ignition 48 seconds, cooling and settling time for the soot 3 seconds, discharging the soot into the collector 2 /2 seconds, safety interval Instead of the controller cylinder described in the example, there may also be used other timing relays of known design.

Instead of a splitting tube in upright position, there may also be employed splitting tubes in a horizontal position. However, in the latter case it is necessary to fit in two more servicing operations for the pressure release in the tube and the discharge of the soot formed by means of a hydrogen blast machine.

For the process of the present invention it is of importance that filling time, filling pressure, cooling time, ignition and discharge periods are always the same. By manual operation these periods cannot be observed to a fraction of a second. Merely by automatic control being independent of human error, uniform qualities of soot are obtained.

The present invention offers the following advantages:

(1) Complete discharge of the soot from the splitting tube, which, owing to the higher pressure in the splitting tube, is etfected much more rapidly than in the case of decomposition with addition of oxygen, and which is carried out without any additional rinsing, merely by the pressure of the hydrogen above the soot, the splitting tube being advantageously installed in an upright position.

(2) Discharge of the soot without previous cooling in the splitting tube immediately after the decomposition of the hydrocarbon or after a short settling time of the soot, with subsequent cooling of the hot hydrogen-soot mixture in a cooler installed behind the splitting tube.

(3) The possibility to impart to the soot, without any aftertreatrnent, the desired bulk weight by means of a reduced cross section of the outlet device or by making the discharge pipe more narrow, for instance, with the aid of nozzles or shutters.

(4) By automatic control of valves and switching operations, the quality of the soot, as regards empyreumatic constituents, its fine granularity, structure and electric conductivity, is influenced favorably and made uniform. In addition, the performance of the apparatus can be increased and the costs for the servicing personnel can be lowered.

We claim:

1. In a process for preparing carbon from acetylene which comprises the steps of introducing the acetylene into a closed elongated substantially vertically arranged container, igniting the introduced acetylene in the absence of oxygen to decompose it into hydrogen and carbon, confining the total decomposition products within said container, permitting all of the carbon to settle out solely by gravity while so confined in the lower portion of the container, suddenly opening a valve at the container bottom a predetermined amount to cause the hydrogen in the container to blow out rapidly thereby discharging completely and solely by this action all of the confined carbon through an outlet, the improvement comprising controlling the bulk density of the carbon by varying the ratio of the efiective internal diameter of the outlet and the effective internal diameter of the container, said effective diameter ratio used being between about 1:1 and 15 :200 to obtain a bulk density correspondingly varying from about 20 to 91 grams per liter without any subsequent treatment, cooling the decomposition products, and' collecting the same separately.

2. The process of claim 1 wherein the bulk density of the carbon is predetermined by adjusting the speed at outlet of the dissociation product.

3. Apparatus for preparing carbon of predetermined bulk density from acetylene, said apparatus comprising an elongated substantially vertically arranged container having an inner wall of highly polished metal, valve controlled inlet means for introducing acetylene as starting material into said container, ignition means within said container for initiating dissociation of said acetylene, outlet means for the container, conduit means associated at one end with said outlet means, cooling and separating means for said mixture of hydrogen and carbon connected to the other end of said conduit, operating means for the outlet means for rapid actuation of said outlet means, and means positioned in said outlet means supporting replaceable discharge opening elements of varying cross-section for adjusting the cross-sectional area of the outlet means relative to the transverse cross-sectional area of said container, the larger the cross-section of the discharge opening element relative to the transverse cross-sectional area of the container, the lower the speed at outlet and the lower the bulk density of the carbon.

References Cited in the file of this patent UNITED STATES PATENTS 872,949 Machtolf Dec. 3, 1907 2,619,410 Fross Nov. 25, 1952 2,658,821 Ammann Nov. 10, 1953 2,690,960 Kistiakowsky et a1. Oct. 5, 1954 OTHER REFERENCES Jones et al.: Bureau of Mines Report of Investigations, No. 4695, May 1950. 

1. IN A PROCESS FOR PREPARING CARBON FROM ACETYLENE WHICH COMPRISES THE STEPS INTRODUCING THE ACETYLENE INTO A CLOSED ELONGATED SUBTANTIALLY VERTICALLY ARRANGED CONTAINER, IGNITING THE INTRODUCED ACETYLENE IN THE ABSENCE OF OXYGEN TO DECOMPOSE IT INTO HYDROGEN AND CARBON, CONFINING THE TOTAL DECOMPOSITION PRODUCTS WITHIN SAID CONTAINER, PERMITTING ALL OF THE CARBON TO SETTLE OUT SOLELY BY GRAVITY WHILE SO CONFINED IN THE LOWER PORTION OF THE CONTAINER, SUDDENLY OPENING A VELVE AT THE CONTAINER BOTTOM A PREDETERMINED AMOUNT TO CAUSE THE HYDROGEN IN THE CONTAINER TO BLOW OUT RAPIDLY THEREBY DISCHARGING COMPLETELY AND SOLELY BY THIS ACTION ALL OF THE CONFINED CARBON THROUGH AN OUTLET, THE IMPROVEMENT COMPRISING CONTROLLING THE BULK DENSITY OF THE CARBON BY VARYING THE RATIO OF THE EFFECTIVE INTERNAL DIAMETER OF THE OUTLET AND THE EFFECTIVE INTERNAL DIAMETER OF THE CONTAINER, SAID EFFECTIVE DIAMETER RATIO USED BING BETWEEN ABOUT 1:1 AND 15:200 TO OBTAIN A BULK DENSITY CORRESPONDINGLY VARYING FROM ABOUT 20 TO 91 GRAMS PER LITER WITHOUT ANY SUBSEQUENT TREATMENT, COOLING THE DECOMPOSITION PRODUCTS, AND COLLECTING THE SAME SEPARATELY. 